X-ray tubes may be used in a variety of applications to scan objects and reconstruct one or more images of the object. For example, in computed tomography (CT) imaging systems, an X-ray source emits a fan-shaped beam or a cone-shaped beam toward a subject or an object, such as a patient or a piece of luggage. The terms “subject” and “object” may be used to include anything that is capable of being imaged. The beam, after being attenuated by the subject, impinges upon an array of radiation detectors. The intensity of the attenuated beam radiation received at the detector array is typically dependent upon the attenuation of the X-ray beam by the subject. Each detector element of a detector array produces a separate electrical signal indicative of the attenuated beam received by each detector element. The electrical signals are transmitted to a data processing system for analysis. The data processing system processes the electrical signals to facilitate generation of an image.
Generally speaking, in CT systems, the X-ray source and the detector array are rotated about a gantry within an imaging plane and around the subject. Furthermore, the X-ray source generally includes an X-ray tube, which emits the X-ray beam at focal point. Also, the X-ray detector or detector array in some systems includes a collimator for collimating X-ray beams received at the detector, a scintillator disposed adjacent to the collimator for converting X-rays to light energy, and photodiodes for receiving the light energy from the adjacent scintillator and producing electrical signals therefrom. In other systems, a direct conversion material, such as a semiconductor (e.g., Cadmium Zinc Telluride (CdZnTe)) may be used.
The X-ray tube, for example, may include an emitter from which an electron beam is emitted toward a target. The emitter may be configured as a cathode and the target as an anode, with the target at a substantially higher voltage than the emitter. Electrons from the emitter may be formed into a beam and directed or focused by electrodes and/or magnets. In response to the electron beam impinging the target, the target emits X-rays.
X-ray tubes are typically configured to maintain a vacuum within the X-tube through which the electron beam travels. For example, in some systems, a portion of the distance between the anode and the cathode may include a length of pipe or tube through which the electron beam travels. The length of pipe or tube may have a diameter of relatively small size to facilitate the use of magnets to create a field within the length of pipe or tube to deflect or position the electron beam. Because of the energy present in the electron beam, the electron beam may cause serious damage to the length or pipe of tube through which the electron beam passes if the electron beam strikes the interior of the length of pipe or tube. For example, if the pipe or tube becomes punctured, breached, or otherwise damaged or compromised, the vacuum within the pipe or tube may be lost and the X-ray tube may not function properly. Repair and replacement of the tube, or a vacuum casing which the tube forms a part of may be time consuming and expensive. The distance from the anode to the cathode (and the length of the pipe or tube through which the electron beam travels) is increased for certain more recently employed X-ray tube designs. Problems associated with a mis-aligned electron beam striking the inside of the pipe or tube occur more frequently and/or are exacerbated by these increased lengths of tubes or pipes through which electron beams travel.